If $x \circledcirc y = 7x-y$ and $x \barwedge y = x-3y$, find $-4 \circledcirc (0 \barwedge 3)$.
Solution: First, find $0 \barwedge 3$ $ 0 \barwedge 3 = 0-(3)(3)$ $ \hphantom{0 \barwedge 3} = -9$ Now, find $-4 \circledcirc -9$ $ -4 \circledcirc -9 = (7)(-4)-(-9)$ $ \hphantom{-4 \circledcirc -9} = -19$.